A wind turbine comprises a rotor, a nacelle and a tower. The rotor comprises rotor blades and a rotor hub.
The wind interacts with the rotor blades and rotates the rotor of the wind turbine. The rotor is connected to an electric generator. The rotation is transferred to the electric generator and the rotational energy is transferred into electric energy in the electric generator.
The rotor is connected to the electric generator. The electric generator is connected to a support structure in the nacelle. The nacelle is connected to the tower of the wind turbine. Flanges are used to establish connections between different parts of the wind turbine, for example between the rotor of the electric generator and the hub, or between the stationary part of the electric generator and a support structure of a direct driven wind turbine.
Due to the weight of the components of a wind turbine, and due to the loads induced into the wind turbine by the wind, static loads and varying loads need to be transferred over the flange connections in the wind turbine.
These loads lead to forces acting on the flange connection and the flanges. The flanges comprise holes that are used with connectors, like bolts or rivets, when the flanges are connected.
The forces acting on the flange connection lead to stress in the area of the holes and the connectors. The stress at the holes and connectors leads to fatigue, to a reduction of the durability, and thus to a reduction of the lifetime of the flange connection.
A reduction in lifetime is unwanted and thus the stress at the holes and the connectors of the flanges in the wind turbine needs to be reduced.